1. Field of the Invention
The invention concerns improved multiple-shelved units particularly adapted for use in greenhouses for supporting growing plants whereby the capacity of the greenhouse to accomodate the plants is greatly increased.
2. Description of the Prior Art
Heretofore units for the purpose referred to above have been developed, as illustrated, for example, by that disclosed in patent to Englert U.S. Pat. No. 3,343,300 issued Sep. 26, 1967. The unit of the patent includes spaced wheels mounted for rotation in vertical planes on a central shaft. Each wheel has a plurality of radially-extending spokes with corresponding spokes of each wheel connected by axially-extending rods. The rods are employed to pivotally support plant-carrying trays. In the operation of the unit, the shaft is rotated to in turn rotate the spokes whereby the rods and the trays carried thereby are moved between lower intermediate and elevated positions. A water-spraying device in a fixed position is provided whereby the plants may be sprayed with water as the shelves approach and pass the spraying device.
Also, units of the general type and for use as disclosed in the above-referred-to patent and including certain basic features employed in the units of the present invention have heretofore been commercialized, the units employing piping for various elements thereof. For example, in such prior units the central rotatable shaft is constituted of a section of metal pipe, the shaft-supporting spaced hub members secured thereto by welding or the like. Each hub member includes a plurality of radially-extending threaded sockets which receive threaded ends of radially-projecting pipe sections which define spokes. An outer threaded end of each spoke carries an elbow into a laterally-extending arm of which a threaded nipple is received with the nipples of the corresponding spokes at the opposite ends of the unit projecting towards each other. Each shelf includes uprights at the opposite ends thereof, the uprights having canted slots for the reception of the nipples, such construction permitting the ready removal and replacement of the shelves. In the use of the unit, watering of the plants carried by the shelves is performed manually.
The shafts of the commercially employed units referred to above have, in some instances, been rotated individually by an associated power source. In other instances, two or more of the units have been positioned in longitudinal alignment with couplings between the shafts. In such case, the power source for causing rotation of the shaft of one of the units also serves to rotate the shaft of the coupled unit or units.
The units of both the prior patented and commercially employed constructions described above present various disadvantages. For example, neither of the plant-watering systems previously employed are efficient in operation. When the spraying system is used, the plants are only momentarily subjected to the spray during their passage therethrough, and also the system necessarily results in the discharge of water onto the floor and other elements of the greenhouse. The manual watering of the plants, on the other hand, is excessively time-consuming. With respect to the unit employing pipes for the spokes, the pipes being secured to the hubs solely by the reception of the threaded ends thereof in threaded sockets of the hubs, an additional disadvantage results from the fact that due to the load carried by the spokes, they frequently break at the thread shoulder.